In this article, we report a case of metabolic coma with acidosis and elevated anion gap. The etiological investigation requires laboratory findings because clinical features are not enough specific in the early stage of intoxication. Measurement of methanol and formic acid, its toxic metabolite, is useful in confirming the diagnosis. The major differential diagnosis to discuss is ethylene glycol poisoning. Methanol poisoning is rare but potentially fatal; the toxicity of methanol is clearly correlated to the degree of metabolic acidosis. Formic acid accumulation is also associated with an increased risk for ocular and neurologic dysfunction. For preventing permanent visual damage, the acidosis should be corrected by antidotal treatment or haemodialysis in severe poisoning.